[ofa-general] Re: iWARP peer-to-peer CM proposal

[Steve Wise]

Sean Hefty wrote:
>> The idea for this "hack" is that the passive side (the side that sends 
>> the MPA response) will hold off posting the ESTABLISHED event to the 
>> rdma-cm ULP until after it receives this 0B Read Request from the 
>> client...
> 
> What is notifying the passive side that the active side has completed a 
> read request, and that it's okay to start sending?
> 

The iwarp provider driver will only post the IW_CM_ESTABLISHED event 
after receiving the read request.  For the Chelsio provider, this will 
require changes to the rnic firmware and the driver/library to support 
all this.

I haven't thought through exactly how this should be implemented.  For 
instance, the provider library poll function needs to deal with this 0B 
read completion and note that it is this special connection setup 0B 
read and thus hide the completion from the user call poll()...


> Also, at least with IB, a QP be configured on creation to always 
> generate a CQ entry for all WRs posted to the send queue.  I don't know 
> if iWarp follows this same model.

After thinking about this more, I think we do want to make this 0B read 
signaled.  Then we can post the IW_CM_ESTABLISHED event on the client 
side when the read request completes.

So from the RDMA application's perspective, the connection never gets 
setup until this 0B read is completed, and that's really what we want...

Steve.